Unraveling the molecular interplay between vimentin and G4-repeats

Vimentin is an intermediate filament protein whose overexpression is associated with epithelial-to-mesenchymal transition (EMT) and cancer progression. This protein is primarily located in the cytoplasm, but it is also found in the nuclear matrix of metastatic cancer cells. Studies identified that the nuclear fraction of Vimentin can bind guanine-rich genomic sites. These sequences can fold into a non-canonical secondary structure of DNA called G4 and they play crucial roles in genome maintenance, replication, and transcription. Here we found that Vimentin is a high-affinity binder of the non-canonical secondary structure of DNA called G4-repeats, which consist of at least two adjacent G4 units. A bioinformatic search for those sequences putatively able to adopt G4-repeat structure within human gene promoters revealed an enrichment of genes associated with EMT, suggesting that the binding of vimentin at G4-repeats may contribute to this process. Among all the identified sequences, we selected the one located within the promoter of the TEAD4 oncogene. We confirmed its G4-repeat folding by biophysical characterization and evaluated its interaction with vimentin. This interaction could suggest a feedback loop between vimentin and TEAD4, both implicated in tumor progression. To understand the rationale behind this interaction, we characterized the unique complex at a molecular level. Structural studies using Hydrogen-deuterium exchange mass spectrometry and circular dichroism revealed significant conformational changes in Vimentin upon G4-repeat binding. Although Cryo-electron microscopy has not yet produced high-resolution structures, the obtained maps offer unprecedented insights into the vimentin tetramer and its complex with G4 repeats. This work paves the way for future research into this molecular interaction mechanism and its potential as a promising target for cancer therapy.